1. Field of Invention
This invention relates in general to particle movement control and, in particular, to a fence for precipitating, depositing, and accumulating matter moved by wind currents to protect roads and facilities from sand encroachment.
2. Description of Related Art
Control of particulate matter, such as sand, is a major concern in many areas of the world. Over one-third of Saudi Arabia, for example, is covered by sand, which has hundreds of sand storms, annually. Facilities, wellsites and roads located in these desert areas suffer from sand accumulation caused by these movements. Over time, sand dunes and sand sheets accumulate, requiring costly excavation procedures.
There are a number of solutions employed to try to prevent such sand accumulation. These solutions include, for example, oil and chemical stabilization, vegetation, barrier fences, and wood slat or fabric sand fences. The concept of a “sand fence” is to reduce the wind speed as it passes through the fence, thereby causing the wind to deposit the sand load around the fence. This is in contrast to other types of fences, such as barrier-type fences, which are typically used to form a barrier to prevent sand or soil migration. The wood slat and fabric “sand fences” are placed at a distance from the facility to be protected, and the deposited sand accumulates at the fence location, thus reducing the amount of sand reaching the facility.
There are a number of disadvantages to the currently used methods. Oil and chemical stabilization will only hold the sand underneath the surface and will not stop it from traveling over the top of the surface. Vegetation typically requires at least two years to become permanently established, requires irrigation, and may be eaten by desert animals. Barrier-type fences, by their nature, quickly become buried, thus rendering them ineffective. Wood slat and fabric “sand fences” are not durable, are susceptible to damage and theft, and are very hard to repair. Further, due to structural and environmental limitations, the wood slat and fabric “sand fences” generally have a maximum height of approximately one meter, and cannot be extended in height. Accordingly, although not as quickly as barrier-type fences, the wood slat and fabric “sand fences” are, nevertheless, often relatively quickly buried by the sand over time, thus rendering them ineffective. This results in a requirement to either excavate the sand or install a replacement “sand fence.” Further, although studies conducted by the inventors revealed that sand moved by wind currents that is subject to being accumulated through use of a sand fence, only extends from between the zero level and about the two meter level, as noted above, such conventional “sand fences” extend only up to approximately one meter, and thus, allow a great deal of sand to be moved, unimpeded, over the top of the conventional “sand fence.” Additionally, the wood needed to build the wood slat “sand fences” often must be imported, or is not otherwise locally available.
Accordingly, recognized by the inventors is a need for a higher, more durable sand fence, configured to maximize both fence service life and sand accumulation volume, that is easy to manufacture, transport, and install, that has low maintenance requirements and is easy to repair, that has material specifications and construction procedures that are easy to standardize, and that does not require extensive material importation.